A feeding guild indicator to assess environmental change impacts on marine ecosystem structure and functioning.

Integrating food web indicators into ecological status assessments is central to developing effective management measures that can improve degraded ecosystems. This is because they can reveal how ecosystems respond to environmental change that cannot be inferred from studying habitat, species or assemblages alone. However, the substantial investment required to monitor food webs (e.g. via stomach contents analysis) and the lack of internationally agreed approaches to assessing them has hampered their development. Inventories of trophic interactions have been collated world-wide and across biomes, and can be applied to infer food web structure and energy flow. Here, we compile a new marine dataset containing 8,092 unique predator–prey interactions from 415,294 fish stomachs. We demonstrate how feeding guilds (i.e. groupings based on diet and life stage) could be defined systematically and in a way that is conducive to their application internationally across ecosystems; and apply them to the North Sea fish assemblage to demonstrate their responsiveness to anthropogenic pressures. We found evidence for seven distinct feeding guilds. Differences between guilds were related to predator size, which positively correlated with piscivory, phylogeny, with multiple size classes of a species often in the same guild, and habitat, as pelagic, benthic and shallow-coastal foraging was apparent. Guild biomasses were largely consistent through time at the North Sea-level and spatially aggregated at the regional level with change relating to changes in resource availability, temperature, fishing and the biomass of other guilds. This suggests that fish biomass was partitioned across broad feeding and environmental niches, and changes over time were governed partly by guild carrying capacities, but also by a combination of covariates with contrasting patterns of change. Management of the North Sea ecosystem could therefore be adaptive and focused towards specific guilds and pressures in a given area. Synthesis and applications. We propose a food web indicator which has been explicitly called for to inform policy via food web status assessment as part of the European Union's Marine Strategy Framework Directive and the indicator toolkit supporting The Convention for the Protection of the Marine Environment of the North-East Atlantic (the ‘OSPAR Convention’)

A two-stage ultrafiltration process for separating multiple components of Tetraselmis suecica after cell disruption

A two-stage ultrafiltration process was applied to the aqueous phase of Tetraselmis suecica after breaking its cell wall by high-pressure homogenization. Microscopic observation revealed that the cells were completely disrupted from 600 bar and cell fragmentation of the cells was also noticeable after 800 bar. In addition, the highest concentration of all the molecules of interest in the aqueous phase was observed at 1,000 bar and a temperature of 46 °C while preserving the integrity of the molecules of interest in the downstream process. After centrifugation, the aqueous phase was submitted to ultrafiltration through two consecutive membranes of different molecular weight cutoffs. Complete retention of starch was possible with a 100-kDa membrane and separation of sugars from proteins with a 10-kDa membrane on the remaining mixture. After testing the process with model solutions, the transmembrane pressure selected was 2.07 bar, which succeeded in retaining starch and pigments during the first part of the process, and proteins during the second part. A linear correlation between the permeate flux rate and the pressure was observed in both parts of the process